Remote control system



March 12, 1957 E. l.. TRIMAN REMOTE CONTROL SYSTEM Original Filed Feb. l5, 1947 March 12, 1957"' E. L. TRIMAN 2,785,391

REMOTE CONTROL SYSTEM original Filed Feb. 15, 1947 s sheets-sheet 2 L s S ma. e \|\[I||I.J TW M mf Mr )w d lll- Q mi.. vm n@ 6v B March 12, 1957 E. TRIMAN REMOTE CONTROL SYSTEM original Filed Feb. 15, 1947 3 Sheets-Sheet 5 nited States Patent- REMOTE CUNTROL SYSTEM Eugene l... Triman, Chicago, Ill.

Original application February l5, 19d?, Seriai No. 728,765, now Patent No. 2,557,581, dated .lune E, 1951. Divided and this application October le, lQStl, Serial No. 190,081

ll Claims. (Cl. 340-206) This invention pertains to signalling and signal con trolled apparatus of general application, but particularly useful in conjunction with remote control systems and the like; this application being a division of my copending application Serial No. 728,765, tiled February l5, 1947, now Patent No. 2,557,581 dated June 19, 1951.

In its broader aspects, the invention has as one of its principal objects the provision of means for transmitting a signal having a certain predetermined characteristic and utilizing the transmitted signal to control a signalmatching means, at a receiving station, which will effect a matching or duplication of the characteristic of the transmitted signal to provide a resultant control voltage or factor useful in the control of some desired instrumentality or apparatus.

More particularly, it is an object of the invention to provide a remote control system utilizing a transmitted signal, for example a radio frequency carrier emitted or modulated as to pulse duration, together with a signalmatching means operating under control of the transmitted signal to provide a matching signal reproducing exactly the selecting characteristic of the transmitted signal, the identity or lack of identity of the matched and matching signals being utilized for control purposes at a receiving station remote from the source of transmitted signals.

A more detailed object of the invention is the provision of a remote control system of general application, and especially useful in one of its adaptations for the control of automatic pbonographs and the like by signals transmitted over a metallic circuit, including commercial power lines, or by space wave propagation, the transmitted signal having a control or selecting characteristic and actuating a local signal generator at the receiving station which is varied in a certain manner under control of the transmitted signal until the locally generated signal is identical in control characteristic to the transmitted signal, the identity or lack of identity between the transmitted and locally generated signals being factors in the actuation of the controlled device, in this instance, the automatic phonograph, to effect for example the selection of a certain phonographic record and the playing thereof.

A further objective aspect of the invention is the provision of remote control apparatus of the class described for automatic phonographs and the like, which utilizes selecting signals transmitted by carrier over a metallic circuit or otherwise, and in which selection is effected as a result of matching or duplication by a local signal generator of the transmitted signal to afford a resultant control voltage or factor.

Another particularized object is the provision of se lecting means actuated responsive to the matching of a local signal with a transmitted selecting signal, both said signals being a phasal function of a standard alternating or pulsating reference voltage such as commonly supplied over commercial power lines.

ln addition to the foregoing are other objects and asf,ice

pects of novelty and utility of detailed and complex character and pertaining to functional and circuit arrangements which are described and explained in View of the annexed drawings, in which:

Fig, 1 is a block diagram of the remote control system in its broader aspects;

Fig. 2 is a block diagram of an embodiment of the system utilizing variable pulse duration as the signal characteristic;

Fig. 2-A is a circuit diagram for a selector-transmitter for the variable pulse system of Fig. 2;

Fig. 2-B is a circuit diagram for a receiving selector unit cooperable with the transmitter of Fig. Z-A.

Broadly, the functional aspects of the novel remote control system are depicted in Fig. l, wherein a characteristic control signal is emitted from the block source l5 and transmitted by any medium to the remote point.

The characteristic of the control signal in the present embodiment is that of pulse duration, derived from what is termed herein as phased modulation; and, in general, it is contemplated that the preferred transmission medium may be a metallic circuit, such as the commercial power lines, for reasons heretofore and hereinafter alluded to, it being understood, nevertheless, that other media are practicable and contemplated, especially space wave propagation at radio frequencies.

As indicated by block 16, Fig. 1, the received signal is utilized to control the operation of a source of matching signal energy, designated as the matching signal generator of block 17, through the medium of a control circuit means 18.

The incoming signal being characteristically modulated as to pulse duration, it is the function of generating means 17 to produce signals the duration of which is progres sively varied above and below some limiting value, and these local signals are fed into a comparor i9, along with the actual incoming signals by-passed along path 2t).

The local generating means 17' will continue to pro duce signals of different pulse length until the generated signal is identical in duration to the incoming control signal, at which time there is in effect a zero resultant control voltage, preferably, which may be utilized in various ways to actuate the controlled device of block 22.

vThe aforesaid control voltage, as represented in block 21, is some function of the incoming and locally generated signal voltages as these are mutually effective in the comparer, it being apparent that the resultant control voltage may be zero or different from zero, for control purposes.

In Fig. 2 there are depicted diagrammaticauy the components of a remote control system utilizing pulse duration as the control characteristic. A forward pulse generator 25 produces pulses having a predetermined duration, as selectively varied for example by the master control means there-indicated, and pulses of this duration are propagated or directed to the remote control point or receiving station by transmitter means 2o. ln conjunction with the forward pulse generator, the master control is depicted schematically as a phase-shifting network, it being contemplated, as will more particularly appear hereinafter, that the limiting values of the pulse duration may conveniently be set between the beginning and end of a single cycle of commercial power line voltage, at 60 cycles for example, and the duration of such pulse may be controlled selectively by applying an etfec tive voltage at an instant during ysaid cycle, determined by said phase-shifting network, to the control grid of a thermionic pulse generator or an oscillator.

The transmitted pulse from the control station is suitably ampliiied by means 27 at the remote point, and rectified in signal detecting unit 28 to provide a posi- :arsenal tive incoming pulse for both control and comparison purposes; and this pulse is fed to a differentiating circuit means 29 and also to -a comparer circuit means 30.

The differentiating means, as will appear more particularly in the circuit description, functions to produce a short triggering pulse for control of the local matching signal generator 32, which pulse is amplified in unit 3l..

The local generating means 32 is preferably a singlecycle multivibrator adapted to produce in rapid succession, short pulses the duration of which may be varied by varying a circuit component, such as the capacity 33, to produce what is preferably referred to as the reverse pulse, which is fed into the comparor circuit means 30, along with the positive incoming pulse component from 'the detector stage 2S.

lf the incoming forward pulse and the locally generated reverse pulse are of substantially identical time duration, a thermionic control circuit or rectifier 34, actuated by the resultant control voltages from the comparor 36, will cause `a master control motor 35 to stop. This motor is coupledy to the reverse pulse generator control or capacity 33 to vary the latter so long as the motor runs in one or the other direction, which it will continue to do so lonf7 as the forward and lreverse pulses are not identical. lt will be apparent that the control motor 35 must always rotate predetermined amounts between opposite, fixed limits corresponding to positions of the capacity control 33 to effect matching of local with incoming signals, by reason of which this motor may also be utilized to control a. desired device, such as a phonograph seleci tor switch or the like.

ln Fig. Z-A is shown a wiring diagram for a selective control unit for transmitting pulses of selectively varied duration in conjunction with a phonograph control system, the transmission medium in this instance being the commercial power lines 40 supplying 60 cycle current to the primary 4l of a power transformer, one secondary winding i2 of which supplies plate potential via lead 43 and R. F. choke 4d to the plate 45 of a thermionic oscillator tube, the plate circuit being completed to the cathode 46 mainly via leads 47, coin switch 48, closed momentarily by deposit of a coin in the usual coin control (not shown) provided for'phonograph selectors, and conductor 49 back to said high-potential secondary winding 42 through the winding S0 of a locking relay and conductor 5l.

The momentary flow of plate current in the aforesaid plate circuit will cause the locking relay to pull up and close its own interlock circuit via contacts 52, normally closed contacts 535-54 and cathode 'lead 47, timing capacity 55 being shunted across relay winding Si) through relay contacts 5d, so that the relay continues to hold up although plate current is llowing only during half-wave intervals of the 60 cycle supply voltage.

The grid circuit of the oscillator tube, from grid 53 connects through grid condenser and leak 59 to one terminal 60 of a tank inductance, the opposite terminal 61 of which is coupled through capacity 62 to plate 45, and via. conductor 63 and line coupling capacity 64 to one side of the power lines 40. This grid circuit is completed to cathode from tap 66 on the tank coil via conductor d'7 and radio frequency capacitor 68 to cathode 46, the tank coil being tuned to the desired R. F. line transmission frequency by shunt capacitor 69.

Normally, contacts 70, ganged with contact 54, are closed to complete a short circuit around grid inductance till-66 via conductors 67A and 7l, as a result of which the oscillation of the aforesaid circuit is prevented until such time as one of the selector push buttons 72A, 72B lZG is depressed for purposes of effecting a phonographic selection.

When the locking relay has its `coil 50 energized as aforesaid, following deposit of a coin, -a mechanical interlock (indicated schematically by the dash-dot line, switches 54, '7.0) is set up by which any of the `push 4 Y buttons 72A 72G depressed will be locked in set o1' closed condition; and as one result of the selective depression and locking-in cf,4sa, the push button 72B, switch contact 5d will be transferred from Contact 53 to contact 53A, and also, contacts 7l? will be opened, lifting the short-circuit around grid inductance oil-66, so that the oscillator circuit may now oscillate during appropriate half-wave intervals of the supply frequency.

As another important incident of setting of selector push button as aforesaid, contacts 73B thereof close, thereby connecting the tank coil cathode lead 67 through a phase-shifting resistor '7d-B, conductor 7S to one terminal of a phase-shift grid-bias secondary winding 76 of the aforesaid power transformer, the remaining terminal of which. winding connects via conductor 77 and series phase-shift capacity 73, conductor 79, and phaseshift resistors 74H, MG 74C to the depressed push button contacts 73B, by reason of which a grid-biasing voltage is applied to conductor 57A from winding 76, the phase of which is shifted (in a predetermined amount dependent upon the values of phase-shifting components 78 and the connection to the resistor network 74B 74H) relative to the plate voltage.

As a result of applying a selectively phased grid bias to the oscillator during intervals of relatively phased oscillation as aforesaid, radio frequency impulses of selected duration are impressed upon the power lines 40 through coupling means or capacities da, 65, to be picked up by remotely situated receiving and selecting apparatus now to be described.

A plurality of selecting pulses of predetermined duration will be impressed upon the transmission medium or power lines following depression of one of the selection push buttons as aforesaid, these pulses following in very rapid succession for a determined length of time considered adequate to assure response at the remote controlled station, said length of time being dependent upon the time required for the timing capacity 55 to discharge, it being recalled that as an incident to depression of a push button, contact transferred to contact 53A, thereby shunting the cathode return i7 around relay winding 5d via contacts 53B and lead 53C to conductor 5l. As soon as the relay falls back, both the electrical and mechanical interlocks set up thereby are broken, with the result that contacts 7i?, controlling oscillation, `and contact 54, are restored to normal condition, awaiting the next coin-operation of the control unit, and the particular push button'which had been depressed and locked down, is freed and normalized.

in Figure Z-B is shown a circuit `diagram of a pulseduration selecting means, wherein the pulse generating and transmitting means :indicated di ammatically in blocks Si@ and 3l apply a selec c at radio freuen-cy, for example, to power lin rrnni which the pulse signals are picked up by .sui ble coupling means, e. tg. the line coupling capacities indicated, and passed through `a suitable amplifying means 82, preferably, before rectification by the usual signal detecting' means S.

The .rectified incoming selecting pulses are fed to -dilerentiating means through coupling transformer 34 said means consisting in this instance of capacity and resistance 36 calculated to give a time constant resulting in a very short pulse for triggering the local pulse generating means, this triggering pulse being coupled via conductors @7 to the gr -cathode cir-cuit, including bias potential means ot biased amplifier means 59.

The differential triggering pulse, 4amplification by the biased amplifying means 39, is applied via conductor @il to the grid 9i, of one of a pair of triodes in the local signal generator, through coupling capacity Z, cathode 93 for this triode being returned to the common ground d.

The local signal-matching generating means `is depicted as a form of single cycle multivibrator in which pulse arcanos changes in the circuit 95 of first triode plate 96 are Icoupled through a variable capacity 97 to the control grid 93 of a second triode, which is coupled through parallel capacity 99 and resistance 1G@ lto `the generator output lead 101, .along with the grid 91 of the first triode. Capacity 97 controls the duration of each pulse generated by this `signal-matching means, responsive to triggering impulses from the ditferentiator, and said capacity is arrange-d to be progressively, and in .a sense retrogressively, varied by means such as the motor 105, which, as will appear, is connected to `run in opposite directions so long as the incoming and locally generated signals do not match in duration.

Means for comparing the locally generated matching signal .and the incoming control signal includes a comparor consisting of a first gas ltriode or Thyratron V1, the control grid 106 of which is coupled through capacity 167, conductor S, to the line side of differentiator capacity 8S, so that the same signal utilized Vfor triggering is impressed upon the grid of the first gas triode to fire the latter, while the local matching signal is yapplied from generator output lead 101 through capacity 109 to the control gri-d 11i) of a second gas triode V2 in the cornparor to re the same. The plates of both triodes V1 and V2 are supplied from a quenching supply voltage source 111 of suitably high frequency, for example about 420 cycles, .adequate to provide rapid restoration of the two comparer triodes in comparison with the pulse requency.

The plates 114 and 115 of gas triodes V1 and V2, respectively, are connected to ,terminals 116 4and 117 of an an-ode supply transformer Whose primary 11S `is connected to the aforesaid quenching supply frequency source 111, secondary connection 117 being a center tap which connects through bridge resistor -means 119 tto said plate 11S and also t-o the cathode 120 of triode V1, said resistor being grounded as at 121, and teach 'bridge resistance section being shunted by capacity 122, while the third terminal of said transformer connects to the cathode 123 of triode V2.

T he outer terminals of the bridge resistor arms connect respectively via conductors 124 and 125 to control grids 126 and 127 of a second pair of gas `triodes T1 and T2 constituting the master motor control unit, so designated Fig. Z-B, said gnids being connected together through the arms of bridge resistor means 129. A biasing voltage supply 130 is connected, positive, to cathodes 131 and 132 of second pair of triodes, and negative to the common connection :of the arms of the second bridge resistor means 129 .and to ground at 133.

The ano-de supply voltage for the plates of the second set of gas triodes is procured from the secondary windings 136 and 13'7 of a transformer whose primary 13S is supplied from the 60 cycle mains, said `windings 136 and 137 having a common center tap connection 139 to ground `and being :respectively connected through motor tiel-d windings 136A and 137A to plates 134 and 135; thus, plate current owing in either triode T1 or T2 will excite the corresponding tield winding of the Reversible Master Motor 105.

By reason of the normal biasing voltage from source 13d, both of the second master control triodes T1 and T2 are normally quenched, so tha-t the motor fields are not excited and the motor 105 is at rest; however, an effective positive grid voltage in either arm of the bridge resistor means 119, 129, 121, 133, will fire the corresponding triode, with a resultant excitation of the corresponding iield Winding 136A or 137A and consequent armature rotation in a certain direction depending upon the poling of the armature supply voltage 14u.

An incoming control signal impressed upon the grid `of comparer triode V1 would cause control triode T1 to lire, and the consequent plate current flow through motor winding 137A would start the master motor in a rst direction, with a consequent progressive change in `the capacity of variable control means or condenser 97 `of Ithe local generator.

The same incoming control signal would trigger said local generator and the pulse generated thereby would be impressed -upon the control grid of the second cornparcr tube V2 in phase with the signal voltage applied to tube V1, so that under the incoming and locally generated pulses, the comparer triodes are fired and restored simultaneously in very rapid succession if the said pulses are identical in length, under which condition, the resultant voltage inthe bridge circuit 119, 121, 129, 133, is effectively Zero, in consequence of which neither control triode T1 or T2 would fire, and motor 105 would be at rest.

However, so long as the incoming and locally generated pulses are of different duration, the Iaforesaid bridge circuit will be in effect unbalanced with ia resultant control voltage that will fire one or the other control triode T1 or T2, and the master motor will lnun until variable control means 97 tunes the local pulse generating means to produce the identical pulse necessary to match the incoming pulse for a zero resultant control voltage in the bridge circuit. ln this connection, it is impor-tant 4to notice that `the direction of rotation of motor is correlated to the operation of generator capacity 97 4and the relative tiring relationship of tubes V1--T1 and V2-T2 such that the relative displacement of capacity 97 will tend to shorten the duration of the local pulse if the latter is too long, and vice versa.

The pulse-duration embodiment .of the .invention hereinabove described in view of Figs. 2, 2A, 2B, may be utilized yto control any desired `device or instrtunentality, preferably by interconnecting such device with the driving link, indicated by the dash-dot line 142, Fig. 2B, which `connects motor 105 with pulse duration control means 97, as Idepicted schematicallyby the block controlled device 143 and link line 144, which steps a phonograph selecting switch and circ-uit of known form, as indicated.

In general, it is important to observe that in this phasedoscillation system there is no reference standard required at the receiving or controlled station, and the transmission can be effected as Well by space-wave propagation as by metallic circuit; and while the control system as applied to phonographs, particularly, is commonly coupled to the 60-cycle power mains, any metallic or other transmission circuit will do provided there is a source of relatively lowfrequency alternating voltage to power the oscillator; and such voltage may be of a frequency other than 60 cycles.

In the foregoing description it will be noticed that the oscillator of Fig. 2A operates only on half-cycles of the 60-cycle A. C. supply; however, it will be apparent to those skilled in the art that the oscillator may also be made to oscillate during the full cycle or some portion thereof which is greater than the half-cycle period, regardless of any phased selecting voltage applied to control the pulse emission of the oscillatr (i. e. to grid circuit 5S).

The maximum period of oscillation of the phasedmodulation oscillator of Fig. 2-A is one cycle; but, as a practical matter, where the source of oscillation is a thermionic tube such as the triode l5-46u58, the applied A. C. plate voltage will be effective to produce oscillation only during a portion of 'the supply voltage cycle, whether this be a half or full-wave operation (as by use of a tube with dual plate and common cathode and control grid in place of the triode of Fig. 2-A).

However, the applied phased-selecting grid voltages are always calculated to modify (and in this sense phasally modulate) the inter-cycle oscillation which actually does occur, so as to determine the effective duration of the oscillatory emission. In this sense, the phased selecting voltages determine in each cycle (or half cycle, or fraction of a cycle) the time length of any pulse or oscillatory emission within a period delimited by the beginning and end of a single cycle of the alternating supply voltage `for the oscillator.

assesses 7 In this sense, therefore, the selecting, signals may he regarded as phased inter-cycle pulses of selectively variable duration.

l claim:

l. In a remote control system of the type utilizing a 60- cycle A. C. power line, forward pulse generating means including oscillator having at least a plate circuit and a grid circuit, said plate circuit energized for half-wave operation from'said power line, means coupling the output olf said oscillator to said power line, in including selecting switches for impressing line-frequency A. C. voltage upon said grid circuit, a phase-shift network electrically associated with said switches and selectively operable to modify the phase angle of the effective voltage impressed upon said grid circuit for the purpose of modifying the time factor characteristic of the output of said oscillator selectively as a phasal function of the power line frequency.

Z, ln a remote control system of thc type utilizing a 6G- cycle alternating current power line as a 'transmission medium, at least; selecting-pulse generating means including an oscillator having at least a plate circuit and a circuit, a tanlt circuit part of said grid and plate circuits, means energizing said plate circuit with alternating voltage from said power line, means coupling the output of said tank circuit to said power line, a et ase-shift network selectively variable to impress control voltages from said line upon the grid of said oscillatorhaving different phasal characteristics corresponding to different selecting signals whereby said oscillator emits pulses of different duration depending upon the phasal characteristics sclected, and means for timing the duration of emission oi any selected pulse signals.

3. A pulse generator for remote control systems cornprising a thermionic oscillator' having at least a grid circuit and a plate circuit, a resonating tank circuit included as part of said grid and plate circuits, means including a relay connecting said plate circuit to an alternating voltage power line through a momentary starting switch responsive to momentary closing of the latter, timing means in circuit with said relay for disconnecting said plate circuit 'from said power line following a determined time interval after closure sai-:l switch, a plurality of selecting switches each operable to connect said grid in a dil erent phase-shift circuit with said power ne, whereby to cause said oscillator' to emit pulses of ditlferent duration responsive to closure of said ltirs mentioned switch, a circuit connection normally preventing oscillation of said Voscillator notwithstanding operation ci said vtiret-mentioned starting switch, said connection modified by operation ot' any said selecting suf `h to permit oscillation following operation of the starting switch, and means coupling the oscillatory output or said oscillator to said power line.

4. Apparatus as defined `in claim and Vfurther characterized by the provision of a locking circuit controlled by said relay responsive to operation ot the latter it said first-mentioned momentary switch is operated, and timing means cooperable with said relay for releasing said locking circuit at the expiration of a predetermined period ot time.

5. ln a remote control system, a selec-ting signal transmitter including an oscillator energized from a source ot alternating voltage derived from a commercial power line, the output ot said oscillator coupled to said line, said oscillator having an input circuit including a phase-shift network and selecting switch means for selectively varying the phasal aspect of a control voltage applied to said input circuit, means coupling said input circuit to said power line for derivation oi a control voltage as aforesaid, a coin-controlled switch operable to energize said oscillator, an interlock switch normally rendering said oscillator ineliective to deliver oscillatory energy to said power line,k and an operative interconnection between said interlock switch and said selecting switch means which renders said interlock switch inelective for normal operation as aforesaid esponsive to a selec ing operation of said selectingy switch means, whereby said oscillator is rendered eective to deliver Yoscillatory energy to said line in phasally modied signal form depending in phasal aspect upon the selected operation or" said selecting switch means,

6. Apparatus deiincd in claim 5 and further characterized by the provision of a timing circuit means coopera le with said coin-controlled switch for determining the period ot time during which said oscillator will deliver signal energy as set forth.

7. A phased-modulation remote control signal transmitter including an oscillator, a reference source of periodic voltage, a thermionic relay including at least a grid, a plate, and a cathode, selectively variable phaseslritting circuit means connected to phasally modulate said oscillator to impress selecting-signal voltages thereon, a plurality of individual selector buttons each operaole to vary the phase-shifting means to select a certain plie-sally characteristic signal, relcasahle lock means automatically locking any said button in operated condition,I electromagnetic means in the plate circuit of said thermionic relay and operable responsive to predetermined plate current low in the latter to release said lock means, means coupling the output ot said oscillator to a transmission agency for communication of said signals to a remote station, a coin-controlled momentary switch for initially energizing said electromagnetic means, releasable locking means cooperahle with said electromagnetic means -for holding the latter locked in operated condition upon coin-operation thereof, circuit connections and oscillator control contacts operated by said electromagnetic means in locked operation for rendering said oscillator etlcctive to emit signalling energy and preventing such emission when said electromagnetic means is nonoperated, circuit connections and momentary contact means controlled hy said electromagnetic rnV` s upon said initial operation of the latter to effect momentary release of said releasable lock means for said buttons, time-delay bias means normally biasing said thermionic relay to inoperative condition, and contact means erated by said electromagnetic means in locked operation as aforesaid to start delay operation ci said bias means responsive to selecting operation of a said button following coin-switch operation ot said electromagnetic means, to nullity said bias and permit current tlow in the plate circuit ot said relay to again actuate said hutton lock means and restore said circuit connections and oscillator control contacts to normal condition with said oscillator ineifective to emit signals and said therinionic relay in non-operating condition and to release said locking means cooperable with the electromagnetic means.

8. A transmitter of pulse-duration high-frequency selecting signals comprising a radio frequency oscillator including a modulation circuit controlling an output circuit and powered entirely hy an alternating supply voltage of low frequency, said oscillator oscillating at most at most at intervals delimited by the beginning and end of each half-cycle of said low frequency voltage, means for deriving selectively phased selecting signal voltages from said supply voltage at any of a plurality or selectively predetermined phase angles relative to the said halfcycle of supply voltage, and means for applying the phased signal voltages to said modulation circuit of said oscillator to permit the oscillation thereoiF for intervals the duration of which is a function ci the relative phase angle thereof.

9. ln a remote control system, a transit er of pulseduration selecting signals comprising a high frequency oscillator including a grid circuit and a plate circuit and energized from an alternating voltage source to oscillare at most only during a halt-cycle of each period oit' said voltage, `a pulse-duration modulating circuit for impressing signal voltages derived from said alternating voltage source upon said grid circuit of the oscillator during said period to modify the duration of oscillation during any period aforesaid, selecting means for shifting the phase of said signal voltages relative to said periodic voltage in said modulating circuit to provide a plurality of different selecting-signal oscillator emissions each distinguished in duration from the others, and means coupling the output of said oscillator to a transmission medium.

10. Apparatus as dened in claim 9 and further characterized by the provision of individual manually-operated selecting switches operable to connect phase-shift components with said selecting means and each operable from a normally released condition to operated condition to determine a certain selecting signal voltage phased as aforesaid, mechanical lock means for holding any said selecting switch in operated condition, electrical lock release means, and a coin-controlled initiating circuit for actuating said lock release means to release previously operated switches and to condition said oscillator for eiective signal emission for a measured time dependently upon coin operation of said initiating circuit, and manual operation of one of said selecting switches.

l1. In a phase-selective signalling system for remote control apparatus, selective signalling means comprising an electron tube oscillator including at least an anodecathode circuit and a control grid circuit therefore; an alternating-current power source of predetermined frequency connected with said anode-cathode and grid circuits to apply a positive operating potential to said anodecathode circuit generated during the normal positive halt"- Wave period of each alternation of said source, and further to apply a control voltage from said source to said grid circuit generated during the same half-wave period and in a sense to suppress oscillatory anode-cathode current tlow; and selectively-operable phase-shifting means interposed in said circuit connecting said grid control voltage to said grid circuit and operable to shift the phase of the grid control voltage to suppress oscillation for periods of selectively different duration within the limits of a said half-wave period at said predetermined frequency.

References Cited in the le of this patent UNITED STATES PATENTS 2,183,725 Seeley Dec. 19, 1939 2,404,101 Schock July 16, 1946 2,404,568 Dow July 23, 1946 2,429,771 Roberts Oct. 28, 1947 2,493,508 Thynell Jan. 3, 1950 

